Physical-chemical properties of biopolymer solutions.

ass. prof. Iryna R. Bekusass. prof. Iryna R. Bekus

LECTURELECTURE

BIOPOLYMERS• Biopolymers are polymers produced by living organisms.

• Since they are polymers, biopolymers contain monomeric units that are covalently bonded to form larger structures.

• There are three main classes of biopolymers based on the differing monomeric units used and the structure of the biopolymer formed:

• polynucleotides, which are long polymers composed of 13 or more nucleotide monomers;

• polypeptides, which are short polymers of amino acids; and

• polysaccharides, which are often linear bonded polymeric carbohydrate structures.

Biological role of polymers• Biopolymers, have a lot functions:• Catalytic effect– enzymes;• As regulators – hormones;• is the storage and transfer of genetic

information.(DNA);• Storage energy (Starch, glycogen);• Protection - immunoglobulin;• Structural (collagen, keratins, fibril).

CLASSIFICATION HMC • Polymers are classified by different

possible:• Classification by source;• Classification by structure;• Classification by synthesis;• Classification by molecular forces.

Classification by source

• Natural (nucleic acids, polysaccharides, protein, natural rubber (polyisoprene));

• Synthetic (polyethelene, teflon, polyvinilchloride, polystyrene).

Classification by structureLinear polymers. In these polymers,

the monomers are joined together to form long straight chains of polymer molecules. Because of the close packing of polymer chains, linear polymers have high melting point, high densities and high tensile (pulling) strength.

Branched chain polymers. In these polymers, the monomer units not only combine to produce the linear chain (called the main chain) but also form branches along the main chain

Three-dimensional network polymers. In these polymers, the initially formed linear polymer chains are joined together to form а three-dimensional network structure.These polymers are also called cross-linked polymers

Classification by molecule form • Globular. • Fibril.

Classification by nature atoms, which are in molecule of polymer

• Carbon contain polymers

• Hetero polymers

• Element organic

• Inorganic

BIOPOLYMERS AS MATERIALS• Some biopolymers- such as polylactic

acid (PLA), naturally occurring zein, and poly-3-hydroxybutyrate can be used as plastics, replacing the need for polystyrene or polyethylene based plastics.

• Some plastics are now referred to as being 'degradable', 'oxy-degradable' or 'UV-degradable'. This means that they break down when exposed to light or air, but these plastics are still primarily (as much as 98 per cent) oil-based and are not currently certified as 'biodegradable' under certain international laws.

• Biopolymers, however, will break down and some are suitable for domestic composting.

Zein is a class of prolamine protein found in maize. It is usually manufactured as a powder from corn gluten meal.

Synthesis of polymers

• Addition polymerization occurs when unsaturated monomers react to form а polymer. It is а specific type of addition reaction.

Condensation Condensation polymers are formed by the head-to-tail joining of monomer units. This is usually accompanied by the loss of а small molecule, such as water.

Properties • Properties HMC solution, which same as

true solutions:• Solutions of high-molecular compounds

are stable as molecular solutions;• Solutions of high-molecular compounds

are convertible. If high-molecular compound was solved that the molecular solution will be farmed. And if this solution to strip to dryness, so high-molecular compound was stat, which can solve again.

• Between high-molecular compound and solvent has not boundary.

Properties HMC solution, which same as colloidal solutions:Size of disperse phase in solutions of high-molecular compounds are same as in colloidal solutions (10-7 - 10-9 m);High-molecular compounds can not permeate through semipermeable membrane;High-molecular compounds slowly are diffused in solutions.Specific properties HMC solution:For solutions of high-molecular compounds are characteristic the swelling and high viscosity

• Swelling it is process solubility high-molecular compound in solvent.

• Swilling degree (α):

• α = (m – m0)/m0 = mp/m0

• or α = (V – V0)/ V0 = VP / V0

• Where: m0 and V0 – mass or volume polymer before swilling;

• m and V – mass or volume polymer after swilling;

• mp, Vp – mass or volume of solvent, which is absorbed polymer.

• Some time used mass-volume swilling degree: α= (V0 – V)/ m = cм3/g

• or α = (V0 – V)100%/m

• Biopolymers (also called renewable polymers) are produced from biomass for use in the packaging industry.

• Biomass comes from crops such as sugar beet, potatoes or wheat: when used to produce biopolymers, these are classified as non food crops. These can be converted in the following pathways:

• Sugar beet > Glyconic acid > Polyglonic acid

• Starch > (fermentation) > Lactic acid > Polylactic acid (PLA)

• Biomass > (fermentation) > Bioethanol > Ethene > Polyethylene

• Many types of packaging can be made from biopolymers: food trays, blown starch pellets for shipping fragile goods, thin films for wrapping.

BIOPOLYMER USES

• One of the few polymers in which the stereochemical structure can easily be modified by polymerizing a controlled mixture of L and D isomers to yield high molecular weight and amorphous or semi-crystalline polymers.

• Properties can be both modified through the variation of isomers (L/D ratio) and the homo and (D, L) copolymers relative contents.

• PLA can be tailored by formulation involving adding plasticizers, other biopolymers, fillers, etc

Polylactic acid (PLA)

Polylactic acid (PLA)

Bacterial fermentation is used to produce lactic acid from corn starch or cane sugar.

Catalytic and thermolytic ring-opening polymerization of lactide (left) to polylactide (right)

Stannous octonateOr tin(II) chloride

Two lactic acid molecules undergo a single esterfication and then catalytically cyclized to make a cyclic lactide ester.

PLA of high molecular weight is produced from the dilactate ester by ring-opening polymerization.

Polymerization of a racemic mixture of L- and D-lactides usually leads to the synthesis of poly-DL-lactide (PDLLA) which is amorphous.

•PLA is considered both as biodegradable (e.g. adapted for short-term packaging) and as biocompatible in contact with living tissues (e.g. for biomedical applications such as implants, sutures, drug encapsulation, etc.).

•PLA can be degraded by abiotic degradation (i.e. simple hydrolysis of the ester bond without requiring the presence of enzymes to catalyze it). During the biodegradation process, and only in a second step, the enzymes degrade the residual oligomers till final mineralization (biotic degradation).

•As long as the basic monomers (lactic acid) are produced from renewable resources (carbohydrates) by fermentation, PLA complies with the rising worldwide concept of sustainable development and is classified as an environmentally friendly material.

Polylactic acid (PLA): Biodegradability

Due to PLA's relatively low glass transition temperature, PLA cups cannot hold hot liquids. However, much research is devoted to developing a heat resistant PLA

Mulch film made of polylactic acid (PLA)-blend bio-flex

Biodegradable cups at a restaurant

Proteins by Function

H2N

O

NH

OH

OR

H2N

O

NH

OH

OR

H2N

O

NH

OH

OR

Polysaccharides• Polymers composed

of sugars• Similar to synthetic

polymers in that primary structure, DP not as fixed as proteins

• Uses include energy storage, component of extra cellular matrix (hyaluronan)

Acidic PolysaccharidesAcidic polysaccharides are a group of poly saccharides that contain carboxyl groups and/or sulfonic esters.

These compounds play an important roles in structure and function of connective tissues. These tissues form the matrix between organs and cells that provides mechanical strength as well filtering the flow of molecular information between cells.

Many connective tissues are made up of collagen, a structural protein, in combination with an assortment of acidic polysaccharides that interact with collagen to form loose or tight networks.

Hyaluronic acid is the simplest acidic polysaccharide present in connective tissueMW of ~ 105 and 107 g/mol and contains 30.000 to 100,000Found in embryonic tissues and specialized connective tissues such as synovial fluid, the lubricant of joints in the body, and the vitreous humor of the eye where it provides a clear, elastic gel that maintains the retina in proper position.

Hyaluronic acid

Swelling and Collapse of Single Polymer Molecules and Gels

Single polymer molecules

If polymer chains are not ideal, interactions of non-neighboring monomer units ( the so-called volume interactions ) should be taken into account. If these interactions are repulsive, the coil swells with respect to its ideal dimensions. If monomer units attract each other, contraction leads to the “condensation” of polymer chain upon itself with the formation of a ”dense droplet” conformation, which is called a polymer globule.

Coil-globule transition

synthetic polymers

Polymers made in industry from chemical substances

Scientists are able to copy structures of natural polymers to produce synthetic polymers trough scientific research

synthetic polymers

many of raw materials for synthetic polymers are obtain from

-> petroleum types of synthetic polymers

plastics fibers elastomers

plastics

Properties of plastics :- Light strong malleable inert to chemical insulators of electricity and heat

fibers

long chain polymers that withstand stretching

example of fibers are :-polyamide nylon, terylenephenol-formaldehyde (PF)acrylic polymers

elastomers

polymer that can regain its original shape after being stretched or pressed

example of elastomers are :-Styrene-butadiene rubber(SBR)Polyisoprene (IR) Polybutadiene (BR) Chloroprene Rubber (CR)

What are the properties of plastics?Plastics are all different, but they show a few general properties:

they do not conduct electricity and are poor conductors of heat

they are unreactive – most are not affected by water or air, and many are not affected by chemicals.

Why is the unreactivity of plastics both useful and problematic?

Their unreactivity makes plastics durable and able to safely contain and protect many substances. However, it also means that they persist in the environment for a long time.

Physical properties of polymers are governed by three main factors:

• Number of monomer units in the chain, N, is large: N >> 1.

• Monomer units are connected in the chain. They do not have the freedom of independent motion (unlike systems of disconnected particles, e.g. low molecular gases and liquids). Polymer systems are poor in entropy.

• Polymer chains are generally flexible.

lined-up chains make plastics dense, rigid and harder to melt(e.g. high-density polyethene).

The properties of a plastics depend greatly on how the polymer chains are arranged:

branching chains make plastics light, soft and easy to melt(e.g. low-density polyethene)

What makes plastics different?

What factors might determine the properties of a plastics?

Temperature, pressure and catalysts affect the length and branching of the polymer chain.

The type of monomer used affects the type of forces between polymer chains.

Additives can ‘lubricate’ polymer chains, join them together with cross-links, or preserve them from decay.

reaction conditions

monomer

additives

Factor Effect

Changing the properties of plastics

Plastic bags are a major source of waste at landfill. British shoppers use over 8 billion of them a year!

Landfill is a convenient method of waste disposal but it is only designed to bury rubbish, not to break it down.

Most plastics are made up of tightly bonded molecules that cannot be decomposed by micro-organisms. These will remain buried at landfill sites for thousands of years without rotting.

The UK has 4,000 landfill sites and it is predicted that the largest of these will become full in less than 5 years.

What happens to plastics in landfill sites?

Thank you for attention